The long term objective of the proposed project is the development of a mouthrinse system capable of maintaining therapeutic levels of fluoride at the tooth surface for a duration of up to 8 hours. Currently available self applied fluoride delivery systems (mouthrinses and toothpastes) maintain fluoride levels for only a few minutes at best whereas the more robust professionally applied treatments such as gels are only applied at the most once every few months. Previous concept demonstration studies by the applicants have shown that the achievement of this objective would result in systems capable of almost completely remineralizing developing carious lesions on a daily basis. The system to be developed will use micronized calcium fluoride particles as prolonged release fluoride source. These particles will be suspended in a polymer solution mouthrinse system designed to maximize the adherence of the particles to the tooth pellicle. The goal of Phase I of this project is to find the optimal system of those tested as measured by the in-vitro ability to maintain therapeutic fluoride levels at tooth surfaces. Phase II will be concerned with a more detailed demonstration of the effectiveness of the chosen system using both in-vitro and human in-vivo models as well as the further refinement necessary to achieve a practical commercial system.